Signal rectifier circuits



Patented Feb. 1940 SlGNAhRECTlFIER o ncm'rs seym our flunhdackson Heights, N. Y., assignor to i Radio Corporation of America, a corporation of i Delaware UNITED smrs PATENT OFFIQE 1 Application May'6','1939, Serial No; 272,081

81 Claims. (or. 250- 20) "My present invention relates tosignal rectifier circuits, and-more particularly to signal detectors of the carrier degenerative type.

i In my copendingapplicatiomserial No. 268,078, filed April 15; 1939, (RCA-16,796) there has been disclosed, and claimed, a diode detector circuit which utilizes a driver stage to feed signal energy thereto", and the driver stage being degenerative for the carrier whereby the diode detector may "utilize a' resistorload of relatively small magnitude. As aresult of such-construction the diode is capableof handling 100% modulated signals without regard to anyloading effect on the tuned circuits feeding the; diode detector.

specificallyjthe driver stage is rendered degenerative in the circuit of the aforesaid application by providing-the signal input circuit of the diode detector in the cathode. circuitof the stage arranged to function as the carrier f'degenerative signal transmission tube. The audio fvoltage component ofthe diode rectifier circuit wasemployed in an audio amplifier networ k following the degenerative stage, whilethedirectcurrent voltage component was utilized for automatic volume control.

After further investigation of the" types of circuits disclosed in my aforesaid application, I have found that the audio -voltage component of the rectified carrier energy canbe amplified in the carrier degenerative driver stage. In this way the driver stage is given an additional function withoutin any way interfering with its previous'ly described functions. r

Accordingly, it may be stated that it is one of the main objects of my present invention to provide a signal rectification network of the diode type, and wherein the signal input circuit of the diode is provided in the cathode circuitof a stage arranged to function as a carrier degenerative transmission tubeg'and the audio voltage component of the rectifier output being amplified by the degenerative stage whereby the latter functions as an audio frequency amplifier.

Another important object of this invention is to provide a driverstagefor a diode rectifier, the signal input circuit of the rectifier being located in the cathodercircuit of the driver, and both the direct current voltage and audio frequency voltage of the rectified signal carrier energy being impressed upon the input control electrode of the driver stage. r

Another objectv of this invention is to provide a signal transmission tube which is degenerative for the signal carrier of receivedrsignals, and

which feeds carrier-energy toiat least one diode entire arrangement being economically constructed and assembled. '1 In the drawing:

Fig. 1 illustrates one circuit arrangement embodying the invention, l

Fig. 2 illustrates a modification wherein separate diode rectifiers are employed to produce the audio frequency voltage and automatic vol ume ic'ontrolbias; r r

Fig. 3 illustrates a modification of the arrangement shown in Fig. 1; and r 1 Fig. 4 illustrates a modification of the arrangement shown in Fig. 3.

Referring nowto the accompanying drawing,

wherein like reference characters in the different] f guresdesignate similar circuit elements, it is assumed that the receiving circuit shown in Fig.

l is that part of a superheterodyne receiver essential to an understanding of this invention.

For examplethe numeral I may denote the inter:

mediate frequency output circuit of the inter- 85 mediate frequency amplifier. The receiver'can be of the type used in the broadcast range of 550 to 1500 kilocycl'es, although the invention is equally applicable to multi-range receivers. Of course, the intermediate frequency amplifi'ermay be preceded by the usual converter network, and

coupled to a resonant circuit 6 which is tuned-to the operating intermediate frequency. The circuit 6 functions as the input circuit of the tube 1, and the latter may be a multi-func'tion tube of the 637 (or 662'?) type. In general, such a tube isaduplex diode-triode, and the triode consists ofcathode 8, control grid 9 and plate l0. The

auxiliary anodes II, I l' cooperate with cathode 8 to provide a pair of independent diodes. Cathode' 8 provides independent electron streams to v plate It) and the anodes lll I. Anodes I l and ll'-are strapped together in this arrangement, 1 i

and function as a. single diode anode.

. it one or more radio frequency amplifiers may precede theconverter. The circuit l is magnetically.

The grid 9 connected to ground through a path including input circuit 6 and diode load resistor it; the condenser 51 shunts the load retransmitted to the subsequent audio'stagesby audio coupling condenser "21!. i

The direct current voltage developed across resistor is is utilized for automatic gain, or volume, control of the receiver. This is accomplished by connecting the signal grids of the signal transmission tubes prior to tube 1 to the anode end of resistor IS. The lead 2!, which includes the filter 22 for suppressing pulsations in the control voltage, connects each prior tube signal grid to the anode end of resistor It. The lead 2! is designated by the letters AVG, and those skilled in the art know that the control voltage, or AVC bias, acts to reduce the gain of each prior tube with signal carrier increase to an extent such that the carrier amplitude at input circuit 5 is substantially uniform over a wide range of carrier amplitude variation at the signal collector of the receiver.

The grid 9 is diod'e-biased in this circuit; that is to say, the direct current voltage across re: sistor it provides the necessary negative. bias for the grid 9. With the arrangement shown full gain and selectivity are. secured from the circuits 'l and 6. Almost the same amount of carrier-voltage appears across-input circuit 6 and'cathode circuit l3-l2. The triode 8--9 l0 is degenerative for the intermediate frequency carrier. The carrier voltage 'developed across tuned cathode circuit lit-42 is applied to the diode anode ll! 5'; the rectified current fiows through resistor Hi to produce the direct current and audio voltages. The audio voltage appearing across load resistor I6 is applied to grid 9. The triode S9li! now acts as an audio amplifier; the amplified audio voltage appears across output resistor H8.

The diode 8-H looks into a low impedance, which is equal to the triode plate resistance divided by the mu of the tube plus 1. The, input impedance of the triode is substantially infinite. The diode 8-l l may look into an impedance as low as 500 ohms. Hence, the load resistor l6 maybe chosen to have a small resistance value.

- loading of the tuned input circuits.

This means that resistor 5- can be chosen for 100% modulation capability without regard to It will now beseen that tube i functions as a carrier-degenerative driver for a diode detector and as an audio amplifier without distortion of the audio signal. At the same time the tube provides the required AVC bias for the receiver.

The arrangement in Fig. 2 differs from that of'Fig. 1 in that anode H is employed to provide the audio voltage forgrid 9, as well. as the negative bias therefor. However, anode I I is util-" ized for providing the AVG bias. Resistor 30, bypassed by intermediate frequency bypass condenser fsl, is connected between anode ll'and the negative biasing source 32. The AVG lead 2i is connected to theanode end-of resistor'30.=

The source 32 provides a delay bias, of any desired value, for the diode rectifier 8-H. W

In Fig. 3, there is shown an arrangement similar to Fig. 2, except that grid 9 receives its negative bias from a biasing source C (not shown) instead of from diode 8-I l. The biasing source is connected to the low potential end of the coil of input circuit 6 through resistor 41. The audio coupling condenser 40 connects the anode end of load resistor IE to the low potential end of circuit 6. It is to be understood that the circuit is otherwise similar to that shown in Fig. 2; the AVG diode 8-H' and its associated circuit have been omitted.

The space current of. triode 89-Ill may provide the negative bias for the grid 9. It is merely necessary to 'insert a resistor 58 in series between coil l2 and ground, the resistor being shunted by an audio bypass condenser 5|. The resistor 4| is grounded, and thus functions as the direct current voltagelconnection between grid 9 and the low potential end of biasing resistor 5!). Thecircuit is otherwise similar to that of Fig. 3. It will be noted that the anode II is biased by the voltage across resistor 50. This will result in delayed detection by diode 8-H. i

While I have indicated and d escribed several systems for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications may be made without departing from the scope of my invention, as set forth in the appended claims.

What I claim is: V a

1. In combination, an electron discharge device including at least a cathode, a signal grid and a' plate, a source of high frequency coupled to the signal grid, a signal-tuned circuit connected between the cathode and a point of relatively fixed potential, at least one anode operatively associated with the cathode and providing a diode having said tunedcircuit as its input circuit, a load resistor connected between the anode and said point, means for impressing on said grid audio voltage developed across said resistor, and an audio load impedance connected to said'plate.

2. In combination, an electron discharge device including at least a cathode, a signal grid and a plate, a source of high frequency coupled to the signal grid, 2. signal-tuned circuit connected between the cathode and a point of relatively fixed potential, at least one anode operatively associated with the cathodeand providing a diode having said tuned circuit as its input circuit, a load resistor connected between the anode and said point, means-for impressing on said grid audio voltage developed across said resistor, and an audio load impedance connected to said plate, and an automatic volumepcontrol connection to said load resistor for utilizing the direct current voltage developed thereacross.

'3. In combination, an electron dischargev device including at least a cathode, a signal grid and a, plate, a source of high frequency coupled to the signal grid, 2. signal-tuned'circuit connected between the cathode and a point of rela-' tively fixed potential, at least one anode operatively associated with the cathode and providing a diode having said tuned circuit as its input circuit, a load resistor connected between the anode and said point, means for impressing on said grid audio voltage developed across said reslstor, an audio load impedance connected to said plate, a second anode associated with the cathode providing a second diode having said tuned circuit as its input circuit, and an automatic volume control connection to said second diode. i

4. Incombination, an electron discharge dey vice including at least a cathode,'a signal grid and a-plate, a source of high frequency coupled to the signal grid, a signal-tuned circuit con-,

nected between the cathode and-a point of relatively fixed potential, at least one anode operatively associated with the cathode and providing a diode having said tuned circuit as its input circuit, a load resistor connected between the anode and said point, means for impressing on said grid audio voltage developed across'said resistor, and an audio load impedance connected to-said plate, said load resistor and tuned circuit being arranged in series betweengthe anode and cathode.

5. In a radio receiver system an electron discharge tube provided with at least a, cathode,

signal grid, plate and auxiliary anode, a signal input circuit connected between the grid and cathode, a. second signal input circuit connected between the cathode and ground, a load resistor connected in series between the anode and ground, an automatic volumecontrol connection to the anode end of the load resistor, and means for impressing the audio voltage developed across the load resistor upon said grid,

6. In a radio receiver system, an electron dis- 1 charge tube provided with at leasta cathode, signal grid, plate and auxiliary anode, a signal input circuit connected between the grid and cathode, a second signal input circuit connected between the cathode and ground, a load resistor connected in series between the 3 anode :and

ground, an automatic volumecontrol connection to the anode end of the load resistor, and means for impressing the audio voltage developed across the load resistor upon said grid, and an audio output resistor connected to said platefor developing thereacross; amplified audio voltage.

7. A signal detector network comprising a signal transmission tube having a tuned circuit f connected in its space current path whereby the tube is degenerative for the carrier, a diode rectifier associated with said tuned circuit for providing audio voltage, and means for impressvoltage, and means for utilizing said direct current voltage for automatic gain control.

SEYMOUR 

